An electrode is a device adapted to pass electric current into and out of an electrochemical cell of an accumulator. Each electrode has an active mass of material, which provides a surface for receiving or donating electrons. The trend in electrode design today is towards electrodes having a porous active mass which presents a larger surface area per unit weight of active mass, resulting in reduced weight and volume requirements for the electrodes overall.
A known method for making lead electrodes involves covering a metallic grid with an active mass of lead containing polytetrafluoroethylene dispersed as a colloid in the active mass. In that process, polytetrafluoroethylene is mixed with water to form an aqueous suspension. The suspension is subsequently mixed with powdered lead oxide to form a paste containing from about 20% to about 40% water by weight. The paste is converted to the active mass of the electrode.
However, the electrodes produced by that previously known method have a relatively small active surface area. Also, the active mass forms only a weak electrical connection with the metallic grid.
Therefore, there is a need for making lead electrodes with a porous active mass, which has a large active surface area and which strengthens the electrical connection between the active mass and a grid. Such a porous lead electrode would lead to electrochemical cells and accumulators which produce more power per unit of weight and also present very low electrical resistance. Accordingly, an accumulator constructed with such electrodes could withstand relatively large surges in power demand and would be useful for powering electric hoists, electric cars, electric trucks and starter motors for internal combustion engines. Accumulators employing such electrodes would also weigh less because they are capable of producing more energy for a given weight.
There exists a need for making porous lead electrodes using simpler technology and producing less waste to pollute the environment than previously known processes. Ideally, such a process would also be suitable for automation so that workers would encounter less exposure to toxic materials such as lead metal.